The present invention relates to a surface mounting part (module) having a configuration with electronic parts mounted on a printed circuit board for providing a module, and mounted on a mother board, such as a voltage controlled oscillator, and in particular, it relates to a structure for downsizing a module.
As shown in FIGS. 4A and 4C, conventional voltage controlled oscillators used in mobile communication devices, such as portable phones, comprise a printed board 20 having a multi-layer structure of a conductor and an insulator, elements constituting an oscillator, such as a resonator and a capacitor, formed inside, and a plurality of other electronic parts 21, such as a capacitor, a semiconductor element, mounted on the surface of the printed board 20. Moreover, as shown in FIG. 4B, a shield case 22 is provided so as to cover the electronic part 21 for preventing the noise radiation from the electronic part 22 to the outside and entrance of the noise from the outside. The shield case 22 is fixed by fitting projection pieces 22a, elongating from the lower opening side rim of the shield case 22, to semi-circular arc-like terminals 23, 24 provided on both side surfaces of the printed board 20, and soldering.
As shown in FIG. 4A, terminal electrodes 26 to 31 to serve as a power source terminal, an input terminal, an output terminal and a ground terminal, are formed on the periphery of the printed board 20. The voltage controlled oscillator is fixed by electrically connecting the terminal electrodes 26 to 31 to a pad 34 on a mother board 33 by reflow as shown in FIG. 4C.
Furthermore, as shown in FIG. 4D, the official gazette of JP-A-6-111869 discloses an embodiment comprising a module with electronic parts 39 mounted on the front and rear sides of a printed board 37. The module circuit board (printed board) 37 disclosed in the official gazette is fixed by soldering to a mother board 42 via block-like terminal members 41 comprising a conductor film formed on the periphery of an insulator.
In order to downsize electronic devices, the mother board 33 needs to be downsized. Therefor, the printed board 20, 37 needs to be smaller for downsizing the module. However, the configuration comprising the electronic parts 21 mounted on one side of the printed board 20 involves a problem in that since the number of the electronic parts 21 to be mounted is set to some extent, the size of the printed board 20 is limited and further downsizing of the module is disabled.
On the other hand, if the electronic parts 39 are mounted on the front and rear sides of the printed board 37 as disclosed in the official gazette, the electronic parts 39 are allotted on the front and rear sides, and thus a problem of the mounting space of the electronic parts can be alleviated. However, the configuration disclosed in the official gazette involves a problem in that a space for attaching the block-like terminal members 41 is required on the rear side of the peripheral part of the printed board 37 in place of lead terminals so as to disturb downsizing. Furthermore, in the case lead terminals conventionally used are used in place of the block-like terminal members 41, also a problem is involved in that a space for connecting the lead terminals is required so as to disturb downsizing.
In order to solve the problems, an object of the invention is to provide a surface mounting part, capable of corresponding to high density mounting of a mother board and capable of achieving a small size.
A first aspect of a surface mounting part comprises electronic parts on both sides of a printed board, wherein terminal electrodes of the electronic parts mounted on the rear side serve as the terminals to be connected with a mother board.
Since the terminal electrodes of the electronic parts mounted on the rear side serve also as the terminals for connecting with the outside of the surface mounting part, a space for attaching a connecting member for connecting the surface mounting part with the mother board is not required so as to enable downsizing of the printed board, that is, downsizing of the surface mounting part.
Preferably, the surface mounting part is a voltage controlled oscillator.
Since the structure of the first aspect is adopted in a voltage controlled oscillator, the voltage controlled oscillator can be downsized, and thus a mobile communication device comprising the same can be downsized as well.
Further, in the surface mounting part, a solder for connecting the printed board and the electronic parts mounted on the rear side is of a high melting temperature type, that is, a high melting point, which is different from the melting temperature of an eutectic solder for connecting with the mother board so as to prevent displacement of the electronic parts used as the terminal electrodes with respect to the printed board.
Furthermore, the terminal electrodes not connected with the mother board, provided in the electronic parts mounted on the rear side of the printed board having the terminals connected with the mother board, are covered with an insulating material.
Since the terminal electrodes not connected with the mother board are covered with an insulating material, insulation can be ensured without the risk of contacting with the conductor pattern on the mother board side.
Moreover, a space between the electronic parts mounted on the rear side of the printed board is filled with an insulating material.
In the case the surface mounting part is soldered on the mother board by reflow, since the solder for fixing the electronic parts on the printed board (in particular, on the rear side) may be melted, a solder having a higher melting point with respect to the solder for fixing the surface mounting part on the mother board is used for fixing the electronic parts on the printed board, displacement of the electronic parts can be prevented, and positioning and fixing can be facilitated.
In the case their melting points are close, the risk of melting is large. If the melting takes place, the electronic parts mounted on the printed board may be displaced. That is, since the pads of the mother board and the printed board are soldered with each other, displacement takes place toward a larger tensile force side. However, according to the configuration of the fourth aspect, wherein a space between the electronic parts mounted on the rear side of the printed board is filled with an insulating material, displacement of the electronic parts can be prevented, and positioning and fixing can be facilitated.
Still further, the electronic parts mounted on the rear side of the printed board have terminal electrodes on both ends, and the terminal electrodes on one end side are connected with the printed board, and the terminal electrodes on the other end are connected with the mother board.
Since the direction linking the terminals of the electronic parts having the terminals connected with the mother board among the electronic parts mounted on the rear side of the printed board is disposed perpendicular to the printed board, the terminal electrodes on the side not connected with the mother board can avoid the risk of contacting with the conductor pattern of the mother board.